Trimod Besta A 01 041 Float Level Switch

Trimod Besta A 01 041 Side-Mounted Float Level switch

The Trimod Besta A 01 041 is a modular horizontal float level switch engineered for liquid level monitoring and limit detection (high/low alarm or pump control) across demanding marine machinery spaces, offshore installations, and land-based process infrastructure.

Operating on a magnetic snap-action principle, the movement of the float on the liquid side is transmitted through a solid, non-magnetic pressure-tight flange diaphragm to the switch element inside the dry enclosure. Because there are no dynamic seals, packing glands, or internal springs exposed to the process fluid, leakage risk is eliminated under high thermal and static pressure cycles.

Technical Specifications

Features

1. Glandless Hermetic Magnetic Coupling: Operates through opposed permanent repelling magnets isolated by a solid stainless-steel diaphragm, eliminating dynamic shaft seals, bellows wear, and fugitive process leaks.
2. High Thermal & Structural Resilience (PN25): Rated for working pressures up to 25 bar and process media temperatures spanning up to 300°C, handling thermal shock cycles in boiler water and thermal oil circuits.
3. Marine-Engineered Metallurgy: Built with AISI 316L (1.4404/CrNiMo) wetted float assemblies and corrosion-resistant die-cast aluminium housing designed specifically for saline marine environments.
4. Invertible High/Low Alarm Operation: Reversing operation from High-Alarm to Low-Alarm is accomplished either through 180° rotation of the complete unit on the counterflange (noting the direction arrow) or by swapping terminal allocations on the internal microswitch.
5. SIL 1 Certified Architecture: Engineered to IEC 61508 standards for safety-critical plant monitoring, low-water cutoff trips, and automated high-level bilge shutoffs.

Terminal Allocations & Wiring Topology

• Terminal 1 (Common – COM): Phase supply (AC) or positive instrument loop feed (+24VDC/30VDC).
• Terminal 2 (Normally Closed – NC): Circuit is established while fluid level is below the actuation point. Contacts snap open when liquid level reaches the fixed 12 mm differential actuation point.
• Terminal 3 (Normally Open – NO): Circuit stays open while fluid level is below the actuation point. Contacts snap closed when float rises through the actuation threshold (standard High Alarm / Pump Start setup).
• Internal Earth Lug (PE): Internal M4 grounding screw bonded directly to the casing frame for electrical earth continuity.

Applications

• Auxiliary Marine Boilers & Economizers: Primary low-water cut-off and high-water feed-pump control under high-pressure saturation conditions.
• Engine Room Machinery Bilges & Sludge Tanks: Early-stage bilge high-level detection and oily-water separator (OWS) automation loops.
• Heavy Fuel Oil (HFO) & MDO Storage: High-level bunker overflow monitoring and service tank daily day-tank replenishment control.
• Marine Stern Tube & Lubrication Systems: Main engine crosshead and sump level failure warnings.
• Closed Condensate Wells & Hotwells: Critical drain tank vacuum and atmospheric condition level tripping.
• Land-Based Industrial Plants: Chemical storage vessels, thermal oil heater circuits, and boiler feed water deaerators.

Frequently Asked Questions

What is the mechanical difference between the Trimod Besta A 01 041 and the A 01 04?

Both models feature the same square 92 mm PN25 mounting flange, 316L stainless steel float, and IP65 aluminium housing. However, the A 01 041 is a compact unit designed with a non-threaded float pivot strictly for direct side-mounting. The A 01 04 includes a mounting boss on the float body that accommodates G1, G2, or G3 extension rods for deeper or top-mounted configurations.

Can the A 01 041 be used for both high-level and low-level alarms?

Yes. The internal microswitch is an SPDT snap-action changeover contact. You can toggle functionality by wiring between Terminals 1 and 3 (contact makes on level rise, suitable for High Alarms and Pump In start) or Terminals 1 and 2 (contact breaks on level rise / makes on level drop, suitable for Low Alarms and dry-run safety trips). The switch unit can also be installed inverted (turned 180°) on its counterflange.

Is the electrical switch compartment sealed from the tank process media?

Yes. The switch operates entirely across a solid, continuous non-magnetic stainless-steel diaphragm using opposed magnetic repulsion. There are no seals, packings, O-rings, or mechanical pivot shafts bridging the wetted process area to the dry electrical housing, ensuring zero fugitive fluid or vapor leakage into the switch compartment.

What is the minimum liquid density required to operate the float?

The fluid must have a specific gravity / density of at least 0.70 kg/dm³ (0.70 SG). This makes it suitable for fresh water, seawater, lube oils, heavy fuel oil (HFO), and marine diesel (MDO). It is not suitable for light liquid petroleum gases (LPG) without using an enlarged, low-density float module (such as the A 01 07 variant).

Can I manually test the float mechanism while the vessel is in service?

Yes. When paired with the optional Trimod Besta test actuator (Type 2382 or 2383) installed onto counterflange 2829.2 or 2831.4, an operator can manually lift and exercise the float from outside the tank to verify emergency shutdown loops without draining the system or opening the vessel.